springboot01-入门

最新推荐文章于 2025-05-13 17:08:25 发布

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最新推荐文章于 2025-05-13 17:08:25 发布

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简介

Spring Boot来简化Spring应用开发，约定大于配置，去繁从简，just run就能创建一个独立的，产品级别的应用。
Spring Boot的产生背景，J2EE笨重的开发、繁多的配置，低下的开发效率、复杂的部署流程、第三方技术集成难度大。
Spring Boot是J2EE一站式解决方案，是整个Spring技术栈的一个大整合，Spring Cloud是分布式整体解决方案

优点

快速创建独立运行的Spring项目以及主流框架集成
使用嵌入式的Servlet容器，应用无需打成war包
starters自动依赖于版本控制
大量的自动配置，简化开发，也可以修改默认值
无需配置XML，无代码生成，开箱既用
准生产环境的运行时应用监控
与云计算的天然集成

微服务

是一种架构风格，一个应用应该是一组小型服务，可以通过HTTP的方式进行互通，每一个功能元素最终都是一个可独立替换你和升级的软件单元

基础以及环境

基础：Spring框架的使用经验，熟练使用maven进行项目的构建和依赖管理，熟练使用Eclipse或者IDEA
环境：jdk1.8、maven3.x、Intellij IDEA 201、Spring Boot 2.0.1.RELEASE

Spring Boot HelloWorld

实现一个小功能，浏览器发送hello请求，服务器接收请求并处理，响应Hello World字符串

创建一个Maven工程(jar)

导入Spring Boot相关依赖

<dependencies>
	<dependency>
	    <groupId>org.springframework.boot</groupId>
	    <artifactId>spring-boot-starter-web</artifactId>
	</dependency>
</dependencies>

编写一个主程序

//来标注一个主程序类，说明这是一个Spring Boot应用
@SpringBootApplication
public class Demo {

    public static void main(String[] args) {
        // Spring应用启动起来
        SpringApplication.run(Demo.class, args);
    }
}

编写相关的Controller、Service

@Controller
public class HelloController {

    @ResponseBody
    @RequestMapping("/hello")
    public String hello() {
        return "hello world";
    }
}

启动主函数，测试

可以在浏览器输入localhost:8080/hello

简化部署

 <!-- 这个插件，可以将应用打包成一个可执行的jar包；-->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

mvn install
java -jar 启动

细节

POM文件

这里的父项目是自己的父项目，自己的pom文件如下

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.zj</groupId>
    <artifactId>springbootstudy</artifactId>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>character-1-springboot-quickstart</module>
    </modules>
    <packaging>pom</packaging>

    <properties>
        <springboot.version>2.0.1.RELEASE</springboot.version>
    </properties>

    <dependencyManagement>
        <dependencies>
            <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-dependencies -->
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${springboot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
</project>

版本仲裁中心

 <dependencyManagement>
        <dependencies>
            <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-dependencies -->
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${springboot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

spring-boot-dependencies是Spring Boot的版本仲裁中心，以后我们导入依赖默认是不用写版本的，没有在spring-boot-dependencies里面管理的依赖还是要生命版本号的

导入依赖

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

spring-boot-starter-web，是Spring Boot的场景启动器，帮助我们导入了web模块正常运行所依赖的jar包
Spring Boot将所有的功能场景抽取出来，做成一个个的starters(启动器)，只需要在项目里面引入这些starter，相关场景的所有依赖都会导入进来，要用什么功能就导入什么场景的启动器

主程序类，主入口类

@SpringBootApplication

@SpringBootApplication：标注在某个类上面，说明这个类是SpringBoot的主配置类，SpringBoot就应该运行这个类的main方法来启动SpringBoot应用

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = {
		@Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
		@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {

@SpringBootConfiguration：SpringBoot的配置类，标注在某个类上，表示这是一个SpringBoot的配置类

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Configuration
public @interface SpringBootConfiguration {

@Configuration：在配置类上标识这个注解，配置类就是配置文件，配置类也是一个组件，@Component

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Configuration {

@EnableAutoConfiguration

@EnableAutoConfiguration：开启自动配置功能，以前我们需要配置的东西，SpringBoot帮我们自动配置，@EnableAutoConfiguration告诉SpringBoot开启自动配置功能，这样自动配置才能生效

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {

@AutoConfigurationPackage

@AutoConfigurationPackage：自动配置包

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import(AutoConfigurationPackages.Registrar.class)
public @interface AutoConfigurationPackage {

@Import，Spring的底层注解，给容器中导入一个组件，导入的组件由AutoConfigurationPackages.Registrar.class

static class Registrar implements ImportBeanDefinitionRegistrar, DeterminableImports {

		@Override
		public void registerBeanDefinitions(AnnotationMetadata metadata,
				BeanDefinitionRegistry registry) {
			register(registry, new PackageImport(metadata).getPackageName());
		}

		@Override
		public Set<Object> determineImports(AnnotationMetadata metadata) {
			return Collections.singleton(new PackageImport(metadata));
		}
	}

这里写图片描述
@AutoConfigurationPackage就是将主配置类(@SpringBootApplication标注的类)的所在包及下面所有子包里面的所有组件扫描到Spring容器

@Import(AutoConfigurationImportSelector.class)

@Override
	public String[] selectImports(AnnotationMetadata annotationMetadata) {
		if (!isEnabled(annotationMetadata)) {
			return NO_IMPORTS;
		}
		AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
				.loadMetadata(this.beanClassLoader);
		AnnotationAttributes attributes = getAttributes(annotationMetadata);
		List<String> configurations = getCandidateConfigurations(annotationMetadata,
				attributes);
		configurations = removeDuplicates(configurations);
		Set<String> exclusions = getExclusions(annotationMetadata, attributes);
		checkExcludedClasses(configurations, exclusions);
		configurations.removeAll(exclusions);
		configurations = filter(configurations, autoConfigurationMetadata);
		fireAutoConfigurationImportEvents(configurations, exclusions);
		return StringUtils.toStringArray(configurations);
	}

这里写图片描述
@Import(AutoConfigurationImportSelector.class)，给容器导入组件AutoConfigurationImportSelector，导入哪些组件的选择器，将所有需要的组件以全类名的方式返回，这些组件就会添加到容器中，会给容器中导入非常多的自动配置类(xxxAutoConfiguration)，就是给容器中导入这个场景所有要的所有组件，并配置好这些组件
有了自动配置类，免去了我们手动编写配置注入功能组件等工作
下面我们来查看一些细节

//一些细节实现
List<String> configurations = getCandidateConfigurations(annotationMetadata,
				attributes);
//点进去这个方法看到
List<String> configurations = SpringFactoriesLoader.loadFactoryNames(
				getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader());
//再点进去看到
String factoryClassName = factoryClass.getName();//这个String的值org.springframework.boot.autoconfigure.EnableAutoConfiguration
return loadSpringFactories(classLoader).getOrDefault(factoryClassName, 	Collections.emptyList());
//点进去loadSpringFactories这个方法
//FACTORIES_RESOURCE_LOCATION这个值META-INF/spring.factories，这个文件在spring-boot-autoconfigure-2.0.1.RELEASE.jar下，在这个文件中查找org.springframework.boot.autoconfigure.EnableAutoConfiguration
Enumeration<URL> urls = (classLoader != null ?
	classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
	ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));

autoconfigure-2.0.1.RELEASE.jar的META-INF/spring.factories的org.springframework.boot.autoconfigure.EnableAutoConfiguration内容如下

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\
org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration,\
org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration,\
org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration,\
org.springframework.boot.autoconfigure.cassandra.CassandraAutoConfiguration,\
org.springframework.boot.autoconfigure.cloud.CloudAutoConfiguration,\
org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration,\
org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration,\
org.springframework.boot.autoconfigure.couchbase.CouchbaseAutoConfiguration,\
org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.ldap.LdapDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.solr.SolrRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.data.web.SpringDataWebAutoConfiguration,\
org.springframework.boot.autoconfigure.elasticsearch.jest.JestAutoConfiguration,\
org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,\
org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,\
org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration,\
org.springframework.boot.autoconfigure.h2.H2ConsoleAutoConfiguration,\
org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration,\
org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,\
org.springframework.boot.autoconfigure.hazelcast.HazelcastJpaDependencyAutoConfiguration,\
org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration,\
org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration,\
org.springframework.boot.autoconfigure.influx.InfluxDbAutoConfiguration,\
org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration,\
org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration,\
org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.XADataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.JmsAutoConfiguration,\
org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.JndiConnectionFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.activemq.ActiveMQAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.artemis.ArtemisAutoConfiguration,\
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\
org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\
org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration,\
org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration,\
org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration,\
org.springframework.boot.autoconfigure.ldap.LdapAutoConfiguration,\
org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration,\
org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration,\
org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\
org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\
org.springframework.boot.autoconfigure.quartz.QuartzAutoConfiguration,\
org.springframework.boot.autoconfigure.reactor.core.ReactorCoreAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.UserDetailsServiceAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.SecurityFilterAutoConfiguration,\
org.springframework.boot.autoconfigure.security.reactive.ReactiveSecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.reactive.ReactiveUserDetailsServiceAutoConfiguration,\
org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.client.OAuth2ClientAutoConfiguration,\
org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,\
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,\
org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,\
org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,\
org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration,\
org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.ReactiveWebServerFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.error.ErrorWebFluxAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.reactive.WebSocketReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketMessagingAutoConfiguration,\
org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration

总结如下，Spring Boot在启动的时候从类路径下的META-INF/spring.factories中获取EnableAutoConfiguration指定的值，将这些值作为自动配置类导入到容器中，自动配置类就生效，帮我们进行自动配置工作；以前我们需要自己配置的东西，自动配置类都帮我们；
J2EE的整体整合解决方案和自动配置都在spring-boot-autoconfigure-2.0.1.RELEASE.jar；

快速创建spring-boot项目

使用Spring Initializer快速创建Spring Boot项目，以IDEA为例
这里写图片描述

选择需要的模块，向导会联网创建Spring Boot项目

默认生成的Spring Boot项目；
主程序已经生成好了，我们只需要我们自己的逻辑
resources文件夹中目录结构如下
static：保存所有的静态资源； js css images；
templates：保存所有的模板页面；（Spring Boot默认jar包使用嵌入式的Tomcat，默认不支持JSP页面）；可以使用模板引擎（freemarker、thymeleaf）；
application.properties：Spring Boot应用的配置文件；可以修改一些默认设置；